Work will continue in trying to improve high resolution visualization and differentiation of protein and lipid systems in cytomembranes, at first particularly in relation to retinal rod outer segment discs and myelin. In part, this will involve studies of differentially extracted, digested or oxidized tissues. These experiments will be coupled with a variety of staining, dehydration, and embedding procedures. It is expected that pilot autoradiographic experiments will be initiated to explore the feasibility of investigating the metabolism of lipid systems in tissues embedded in the new, water-containing, polar plastics. The initial work would be done with retinal rod segment membranes. New insights that have especially developed in the last year concerning aldehyde fixation and artifacts inherent in conventional dehydration procedures suggest that it would be well worthwhile to reopen active investigation on the extent and character of the extracellular compartment of the brain. Current procedures may be expected to permit the retention of more nearly normal spatial relationships than has been conventionally possible. A considerable file of micrographs of a variety of tissues and cells embedded in water-containing, polar plastics has accumulated with very well preserved membrane systems. It is intended that these along with new material be accurately measured and compared with the thought that these will provide far more accurate data than currently exists in the literature.